Support fastboot variable battery-soc-ok

Bug: 79480454
Test: fastboot getvar battery-soc-ok

Change-Id: Icfd70a71f1598e437316d4b8f895fd851516febb
Merged-In: Icfd70a71f1598e437316d4b8f895fd851516febb
(cherry picked from commit 9a1203b7acf7cf3a09ccec022c4698c994143bbd)
diff --git a/fastboot/constants.h b/fastboot/constants.h
index 2eaf006..705da33 100644
--- a/fastboot/constants.h
+++ b/fastboot/constants.h
@@ -63,3 +63,4 @@
 #define FB_VAR_VARIANT "variant"
 #define FB_VAR_OFF_MODE_CHARGE_STATE "off-mode-charge"
 #define FB_VAR_BATTERY_VOLTAGE "battery-voltage"
+#define FB_VAR_BATTERY_SOC_OK "battery-soc-ok"